In motor vehicles, the actual vehicle speed is calculated on the basis of the individual wheel speeds or wheel rotational speeds, among other things. However, it is possible to accurately calculate the vehicle speed only in a state in which at least one wheel rotates in the linear range of the mu slip curve, and the wheel speed may thus be transmitted linearly to the freely rolling wheel speed which corresponds to the vehicle speed.
In an all wheel drive vehicle, all wheels may be subject to slipping during an acceleration operation, which makes it considerably more difficult to calculate the vehicle speeds. In the presence of traction slip, an attempt is therefore made to brake the wheels with the aid of diagonal brake interventions in such a way that the freely rolling speeds of the wheels may be calculated to thereby infer the vehicle speed. However, the total driving torque is reduced by braking the wheels. This is noticeable to the driver as deceleration, which is frequently not desirable.
An object of the present invention is therefore to improve the known methods for determining the vehicle speed, and a deceleration of the motor vehicles is to be minimized, in particular.